Kinetic stent

ABSTRACT

The disclosed stent is formed of an elongate, flexible duct having a very thin wall and a preformed diameter, length, and shape. The stent is constructed of a woven tubular structure of multiple strands or elements. The woven tubular structure is thermally set to a predetermined diameter and length, so that the “at rest” or natural condition of the tubular structure is predictable. A retention or holding member can be formed at one or both of the ends of the stent. This retention member can be reduced in diameter for insertion into the body passage. The woven tubular structure provides a path for fluids to flow in and around the stent, while a patent lumen is being developed. The woven tubular structure allows the stent to be extended or stretched over a guidewire or other noncompressive member, to thereby reduce the diameter of the stent for insertion of the stent into a body passage.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to stents for use insupporting and maintaining an open lumen within a body passage or vesseland, more particularly, to stents configurable between large and smalldiameters.

[0003] 2. Description of Related Art

[0004] Tubular prosthesis, which are commonly referred to as stents, areused to reinforce or strengthen body passages or vessels. Occluded,collapsed, or compromised body passages, such as blood vessels,esophagus, tracheas, gastrointestinal tracts, bile ducts, ureters, andurethras, can all benefit from stents. These body passages can becomeoccluded, collapsed, or compromised from disease, trauma, or fromspecific surgical procedures upon the wall of the body passage.

[0005] Prior art stents typically comprise a length of plastic tubularmaterial, having a number of side holes disposed along the length of theplastic tubular material. U.S. Pat. Nos. 4,913,683, 4,643,716,5,282,784, 4,957,479, 4,931,037, and 5,364,340 describe stents generallyconstructed in this manner. Each of these stents basically comprises afixed diameter and, therefore, is nonresponsive to the specific diameterof a vessel.

[0006] A prosthesis or stent capable of expanding to appropriatediameters, along the length of the stent, can provide advantages overfixed-diameter stents. Self-expanding stents are disclosed is U.S. Pat.Nos. 5,026,377 and 5,078,720, both issued to Burton et al., U.S. Pat.No. 5,019,085 issued to Hillstead, U.S. Pat. No. 4,969,458 issued toWicktor, and U.S. Pat. No. 5,041,126 issued to Gianturco. Theseself-expanding stents are typically held in a contracted conditionduring insertion into the body passage or vessel and, after beingpositioned within the passage or vessel, released to expand fully. Thestents of Wicktor and Gianturco comprise coiled or looped wires, whichare unable to contact the entire surface of the interior wall of theeffected vessel. The Hillstead stent incorporates a multiple-loop wirestructure, which suffers from the same deficiencies associated with theWicktor and Gianturco stents. U.S. Pat. No. 5,507,767, issued to Maedaet al., discloses a self-expanding stent that employs a plurality ofstraight stainless steel wire sections, separating a plurality of bends,that may be adjusted and set to fit a particular anatomy or condition.U.S. Pat. No. 5,476,505 issued to Limon discloses a coiled stent forintroduction into a body passage at a first diameter and subsequentexpansion within the body passage to a second diameter. This coiledstent relies on a procedure for holding a coil in a tightly woundcondition during insertion of the coiled stent. U.S. Pat. No. 5,409,019issued to Wilk discloses a stent, which surrounds a balloon, so that thecollapsed balloon, upon expansion, can expand the stent. U.S. Pat. Nos.5,078,720 and 5,026,377 issued to Burton et al. describe a combinationof a self-expanding braided stent and an instrument for deployment orretraction of the stent. The instrument for deployment or retraction ofthe stent includes a tubular sleeve, which surrounds and compresses thebraided stent. This surrounding tubular structure, requires that anadditional wall thickness, corresponding to a thickness of the tubularsleeve, be added to the device during placement. Consequently, ashortcoming of the Burton et al. invention is that the placement of thedevice is the time when the lowest profile or smallest diameter isrequired.

[0007] A need remains in the prior art for a prosthesis or stent whichcan be placed accurately into a low-profile or small-diameter conditionand which can expand in diameter to a predictable size with apredictable pressure applied to an interior surface of the vessel wall.A need also exists in the prior art for a stent having a retentionfeature for maintaining the stent in a preferred position within thebody passage. Additionally, a need exists in the prior art for a stenthaving a diameter, which is capable of responding and changing to thedevelopment of the lumen of the vessel or passage.

SUMMARY OF THE INVENTION

[0008] The stent of the present invention can be introduced into a bodypassage or vessel in a low profile or small diameter and, subsequently,expanded to a large diameter. The stent can be inserted into the bodypassage over a guidewire or small gauge catheter in the small diameterconfiguration. After the guidewire or small gauge catheter is removed,the stent is transformed into the large diameter configuration, whichstimulates the reactive nature of the body passage to thereby developor-maintain a patent lumen. The stent is able to provide maximumcommunication and flow of fluids from one surface of-the stent to theother surface of the stent.

[0009] The stent of the present invention is formed of an elongate,flexible duct having a very thin wall and a preformed diameter, length,and shape. The stent is constructed of a woven tubular structure ofmultiple strands or elements. The woven tubular structure is thermallyset to a predetermined diameter and length, so that the “at rest” ornatural condition of the tubular structure is predictable. A retentionor holding member can be formed at one or both of the ends of the stent.This retention member can be reduced in diameter for insertion into thebody passage. The woven tubular structure provides a path for fluids toflow in and around the stent, while a patent lumen is being developed.The woven tubular structure allows the stent to be extended or stretchedover a guidewire or other noncompressive member, to thereby reduce thediameter of the stent for insertion of the stent into a body passage.

[0010] According to one aspect of the present invention, a stent for usein a body passage includes an expandable tube having a proximal tubeend, a distal tube end, and a lumen extending from the proximal tube endto the distal tube end. The expandable tube is configurable between alarge-diameter relaxed state and a small-diameter tension state. Theproximal tube end and the distal tube end are separated by apredetermined distance when the expandable tube is in the large-diameterrelaxed state, and the proximal tube end and the distal tube end areseparated by a second distance, which is larger than the predetermineddistance, when the expandable tube is in the small-diameter tensionstate. A retention member is integrally formed with the expandable tubeand is located just proximally of the distal tube end. The retentionmember has a large-diameter relaxed shape and a small-diameter tensionshape, and has a retention-member diameter, in the large-diameterrelaxed shape, which is greater than an expandable tube diameter of theexpandable tube, when the expandable tube is in the large-diameterrelaxed state. The stent further includes activating means adapted forincreasing a distance between the proximal tube end and the distal tubeend, to thereby change the expandable tube from the large-diameterrelaxed state to the small-diameter tension state. The activating meansis also adapted for changing the retention member from thelarge-diameter relaxed shape to the small-diameter tension shape, byincreasing a distance between the proximal tube end and the distal tubeend. The activating means includes a compression tube, which is adaptedfor fitting within the lumen and for contacting the distal tube end. Thecompression tube is further adapted for applying a distal force onto thedistal tube end when a proximal force is applied to the proximal tubeend. Application of both the distal force and the proximal force changesthe expandable tube from the large-diameter relaxed state to thesmall-diameter tension state, and removal of both the distal force andthe proximal force changes the expandable tube from the small-diametertension state to the large-diameter relaxed state.

[0011] According to another aspect of the present invention, a stentincludes a stent body formed of a braided material and an enlargeddiameter retention member adjacent to the stent body and integrallyformed with the stent body of the braided material. The large-diameterretention member is disposed near a distal end of the stent andcomprises a cone shape. The stent further includes a rigid collar at adistal end of the cone-shaped retention member. The rigid collar definesan aperture. The stent includes a compression sleeve adapted for fittingwithin the stent body and for contacting the rigid collar. The stent isconfigurable into the insertion configuration by application of a distalforce on the rigid collar by the compression sleeve, and is configurableinto the stent configuration by removal of the distal force from therigid collar. The stent further includes a guidewire adapted for fittingwithin the stent body and through the aperture. The retention member mayalso include a number of convolutions disposed on the stent body. Theseconvolutions may cover a majority of the surface of the stent.

[0012] According to a further aspect of the present invention, aretention member for use in combination with a stent includes a tubulartrunk formed of a braided material and a radially increasing portionformed in the braided material. The radially increasing portion isdisposed adjacent to and integral with the tubular trunk, and extendssubstantially perpendicularly to a surface of the tubular trunk around acircumference of the tubular trunk. The retention member furtherincludes a radially decreasing portion formed in the braided materialand disposed adjacent to and integral with the tubular trunk. Theradially increasing portion and the radially decreasing portion maycomprise a cone shape, a convolution, or a combination thereof.

[0013] A method of accessing a body passage according to the presentinvention includes a step of converting a stent into a long-length,small-diameter insertion configuration by applying tension between aproximal end of the stent and a distal end of the stent, to therebyincrease a distance between the proximal end of the stent and the distalend of the stent. The stent is then inserted into a body passage of apatient and moved through the body passage to a desired location. Thestent is then converted into a small-length, large-diameter stentconfiguration by removing the tension, to thereby decrease the distancebetween the proximal end of the stent and the distal end of the stent.

[0014] A method of making a stent, which is transformable between alarge-diameter configuration and a small-diameter configuration, beginswith providing a woven tubular structure. The tubular structure isplaced over a forming tool, which comprises a cylindrical body having afirst diameter and a second diameter. Once the stent is formed, thestent will be transformable from the large-diameter configuration to thesmall-diameter configuration upon application from a compression sleeveof a distal force onto a distal end of the stent. The first diameter ofthe cylindrical body corresponds to the large-diameter configuration,and the second diameter of the cylindrical body is smaller than adiameter of the compression sleeve. After the stent is placed over theforming tool, the stent is irradiated with thermal energy, to therebyset a diameter of a portion of the woven tubular structure to the firstdiameter and to set a diameter of a distal end of the woven tubularstructure to the second diameter. At a final step after the irradiatingstep, the resulting structure is removed from the forming tool. Theforming tool may include a cone-shaped portion near a distal end of thecylindrical body, and the second diameter may correspond to a diameterof a guidewire. The irradiating step can be preceded by a step offolding a portion of the woven tubular structure, located proximally ofthe cone-shaped portion, proximally upon the forming tool to therebyform a retention member.

[0015] According to another method of the present invention, the formingtool comprises a cylindrical mandrel having both a first cone-shapedportion near a distal end of the cylindrical mandrel and a secondcone-shaped portion near a proximal end of the cylindrical mandrel. Theirradiating step is preceded by a first step of folding a portion of thewoven tubular structure, located proximally of the first cone-shapedportion, proximally upon the mandrel to thereby form a first retentionmember, and a second step of folding a portion of the woven tubularstructure, located distally of the second cone-shaped portion, distallyupon the mandrel to thereby form a second retention member. The step ofremoving the resulting structure from the cylindrical mandrel isfollowed by a step of cutting the resulting structure in half, tothereby bisect the resulting structure into two stents.

[0016] The present invention, together with additional features andadvantages thereof, may best be understood by reference to the followingdescription taken in connection with the accompanying illustrativedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic view of the stent of the present inventiondirected to pass through a ureter between a kidney and a urinarybladder;

[0018]FIG. 2 is a side view of the stent in a radially expandedcondition;

[0019]FIG. 3 is a side view of the stent in a radially compressed andlongitudinally extended condition;

[0020]FIG. 4 is a side view of the stent of the present inventionshowing an introducer assembly;

[0021]FIG. 5 is a cut away view of the stent positioned over anintroducer assembly;

[0022]FIG. 6 is a cross-sectional view taken along the axis of both thestent and the introducer assembly;

[0023]FIG. 7 is an enlarged view of the retention member of the stentaccording to the present invention;

[0024]FIG. 8 is a view of one embodiment of the stent of the presentinvention having-convoluted sections at opposing ends of the stent body;

[0025]FIG. 9 is a view of one embodiment of the stent of the presentinvention having convolutions along the length of the stent body.

[0026]FIG. 10 is a view of a material suitable for the construction ofthe stent;

[0027]FIG. 11 is a view of a forming tool or mandrel being used to formthe stent of the present invention;

[0028]FIG. 12 illustrates the use of a mandrel or forming tool and theuse of heat to set the material of the stent to a preferred embodiment;FIG.

[0029]FIG. 13 is a view of one embodiment of the stent having a tetherat one end;

[0030]FIG. 14 is a view of one embodiment of the stent of the presentinvention having a severable mid section;

[0031]FIG. 15 is an end view of the stent in an elongated conditionwithin a body passage or vessel;

[0032]FIG. 16 is an end view of the stent in an expanded conditionwithin a body passage or vessel;

[0033]FIG. 17 is an illustration of the forces applied outwardly fromthe axis of the stent and against the wall structure of the body passageor vessel;

[0034]FIG. 18 is a cut-away view of the stent within a body passage orvessel in an expanded condition;

[0035]FIG. 19 illustrates the relative length to diameter feature in anexpanded condition of the stent;

[0036]FIG. 20 illustrates the relative length to diameter feature in anextended condition of the stent;

[0037]FIG. 21 illustrates the relative length to diameter feature in anintermediate condition of the stent.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0038] Turning to FIG. 1, a stent or prosthesis 30 according to thepresently preferred embodiment is illustrated having a proximal tube end32 and a distal tube end 34. The stent body 36 is shown within a bodypassage or vessel 38, such as a ureter. The stent body 36 extends withinthe ureter 38 between a kidney 40 and a urinary bladder 42. The stentbody 36 of the present invention is sized and configured to exert acompressive force against the interior surface 45 of the body passage38. In the presently preferred embodiment, the stent 30 comprises aretention member 48 at the distal tube end 34. The stent 30 of theembodiment shown in FIG. 1 comprises a ureteral stent, which is adaptedfor developing or maintaining a patent lumen in the ureter 38 betweenthe kidney 40 and the urinary bladder 42. The stent 30 facilitatespassage of fluid in, through, and around the stent body 36 from thekidney 40 to the urinary bladder 42.

[0039] The stent of the present invention preferably comprises a wovenmaterial, which can be elongated and contracted. FIG. 2 is a side viewof the stent 30 in a contracted, radially expanded condition. Thecondition illustrated in FIG. 2 corresponds to an “at rest” or naturalcondition of the stent 30. The lumen of the stent body 36 is fullydeveloped along the length of the stent body 36, narrowing only at thedistal tube end 34. The retention member 48, which forms a cuff orenlargement sized and configured to engage a portion of an organ orpassage, has an enlarged diameter in the natural condition shown in FIG.2. The retention member 48 assists in maintaining the stent 30 withinthe body passage 38, as illustrated in FIG. 1, for example.

[0040]FIG. 3 illustrates the stent 30 in a stretched, radiallycompressed and longitudinally extended condition. The stent body 36 ispreferably reduced in diameter in order to facilitate placement of thestent 30 into a body passage 38. When the stent 30 is stretched alongits axis, the diameters of the stent body 36 and the retention member 48are significantly reduced to facilitate a low profile configuration forinsertion into the body passage 38. As presently embodied, the stent 30is placed into the low profile condition by application of a tensileforce applied to both the proximal tube end 32 and the distal tube end34.

[0041] As illustrated in FIG. 4, a compression sleeve 60, having aproximal end 62 and a distal end 64 (FIG. 5), can be inserted into alumen of the stent 30. The compression sleeve 60 is preferably insertedinto the lumen of the stent 30, until the distal end 64 of thecompression sleeve 60 contacts the distal tube end 34 of the stent 30.After this placement, the proximal tube end 32 of the stent 30 can bedrawn proximally, relative to the compression sleeve 60, to therebyfacilitate elongation of the stent 30. In other words, since the distalend 64 of the compression sleeve 60 cannot pass through the narrowaperture of the distal tube end 34, movement of the proximal tube end 32proximally will lengthen the stent 30. As the stent 30 increases inlength, the diameter of the stent 30 decreases. The reduced diameter ofthe stent 30 facilitates a less-intrusive insertion of the assembly intoa body passage 38.

[0042] A guidewire 70, having a proximal end 72 and a distal end 74, maybe placed within the compression sleeve 60. The guidewire 70 provides ameans for establishing a track, so that the stent 30 and compressionsleeve 60 may be advanced along the guidewire 70 to a desired locationwithin the body passage 38, with the stent 30 in an elongatedconfiguration. After the stent 30 is moved to the desired location, theproximal tube end 32 of the stent 30 is released or relaxed, to therebyallow the proximal tube end 32 to move distally, resulting in anenlargement of the diameter of the stent 30. According to the presentlypreferred method of insertion, the guidewire 70 is placed within thebody passage 38, and the stent 30 is then placed over the proximal end72 of the guidewire 70. Next, the compression sleeve 60 is placed overthe proximal end 72 of the guidewire 70 and into the stent body 36.

[0043]FIG. 5 illustrates a cut-away view of the stent 30 positioned overboth the compression sleeve 60 and the guidewire 70, and FIG. 6illustrates a cross-sectional view of the assembly shown in FIG. 5. Asillustrated in FIGS. 5 and 6, the compression sleeve 60 fits between thestent 30 and the guidewire 70. The opening at the distal end 34 of thestent 30 does not permit the distal end 64 of the compression sleeve 60to pass through. This configuration permits the stent 30 to be stretchedlengthwise, as the proximal end 32 of the stent 30 is extendedproximally along the surface of the compression sleeve 60. At fullextension, the profile of the stent 30 exceeds the outside diameter ofthe compression sleeve 60 by the thickness of the wall of the stent body36. This extended/compressed relationship exists as long as a holdingforce is maintained between the proximal end 32 of the stent 30 and thecompression sleeve 60. When this force is removed, the stent 30 assumesan “at rest” or expanded profile.

[0044]FIG. 7 illustrates an enlarged view of the retention member 48 ofthe presently preferred embodiment. The retention member 48 preferablycomprises an enlarged diameter capable of engaging a portion within avessel or organ, to thereby prevent the stent 30 from migrating orslipping from a desired position or location within the vessel or organ.The distal ring 81 of the retention member 48 is preferably sized andconfigured to prevent the compression sleeve 60 (FIG. 5) from passingtherethrough. The distal ring 81 preferably comprises-a thermally fusedor melted portion of material fibers 84 from which the stent 30 iswoven. The distal ring 81, however, may be formed in other ways and/orcomprise other materials. In the presently preferred embodiment, theretention member 48 comprises the shape of a cone 87 having a smalldiameter portion 89 distally located from a large diameter portion 92.The retention member 48 preferably comprises a substantially folded lipsection 95 and a substantially folded angular portion 98 providing atransition between the stent body 36 and the retention member 48.

[0045]FIGS. 8 and 9 illustrate stents 30 having series of convolutions100, 102, and 104 formed along the stent bodies 48. These convolutions100,; 102, 104 can operate to add strength to the retention members 48and 107. The convolutions 100, 102, 104 also provide additional strengthto the stent bodies 36 for resisting compression in much the same way ascorrugated tubing resists kinking and compression. Additionally, theconvolutions 100, 102, 104 assist in providing traction within the lumenof a body passage 38 and are sized and configured to be reduced inprofile in the same manner as the stent body 36 by the application oftraction or tension upon the stent body 36.

[0046] As illustrated in FIG. 10, the stent 30 is formed from an initialwoven tubular structure 111, which preferably comprises a thermoplasticmaterial or mesh. This construction begins by weaving or braiding aplurality of individual or groups of individual fibers or elements 84into a tubular stent body 36. Desired characteristics may be developedwithin this construction for providing ratios of expansion to extension,as is known in the art.

[0047] After the woven tubular structure 111 is generated, the woventubular structure 111 is placed onto a forming tool or mandrel 113having a proximal end 115 and a distal end 117. The mandrel 113 servesas a form in setting the thermoplastic material of the woven tubularstructure 111. In the presently preferred embodiment, the forming tool113 comprises a first diameter near the proximal end 115 and a seconddiameter near the distal end 117. The first diameter represents thedesired maximum deployed or expanded diameter of the stent body 36 whenthe stent body 36 is within a body passage or vessel 38, and the seconddiameter corresponds to the diameter of a conventional guidewire 70(FIG. 6) but smaller in diameter than the diameter of the compressionssleeve 60 (FIG. 6).

[0048] The woven tubular structure 111 of the stent 30 is foldedproximally upon the forming tool 113 to thereby form the retentionmember 48. As shown in FIG. 12, the forming tool 113 and the woventubular structure 111 are next exposed to radiation 121 from a heatsource or an oven preferably at a temperature sufficient to set thematerial of the woven tubular structure 111 to the preferred condition.In the presently preferred embodiment, the material comprises athermoplastic, such as a polyester or nylon, since these materials allowfor the development of a permanent, thermally set condition.Additionally, the distal tube end 34 and the distal ring 81 arepreferably fused or melted to form a solid ring or collar which providessupport for the compression sleeve 60. As a secondary operation, aproximal portion 123 of the stent body 36 may be coated with anelastomeric material to thereby provide stability at the proximalportion 123.

[0049]FIG. 13 illustrates a stent 30 having a tether 130 attached orformed at the proximal tube end 32 for assisting in the placement or theremoval of the stent 30 from a body passage 38.

[0050]FIG. 14 illustrates a stent having a first retention member 48 anda second retention member 136 located at an end opposite from-the firstretention member 48. The stent having the two retention members 48, 136may be used as is or, alternatively, the stent may be cut at a preferredlocation 138 to form two individual stents 140 and 142.

[0051]FIG. 15 illustrates an end view of the stent 30 of the presentlypreferred embodiment within a body passage 38. The stent 30 isillustrated in an extended, small diameter condition over both thecompression sleeve 60 and the guidewire 70. FIGS. 16 and 17 illustratethe stent 30 in a large-diameter relaxed state. The guidewire 70 and thecompression sleeve 60 may be removed at this time. The stent body 36exerts a constant outward pressure 151 upon the interior surface 45 ofthe body passage 38. This outwardly directed radial pressure, along withthe naturally occurring tendency for the intimal tissue to move awayfrom a foreign body, combines to enlarge and/or maintain the lumen ofthe body passage 20.

[0052] An enlarged view of a body passage 38 is provided in FIG. 18 witha stent 30 of the presently preferred embodiment fully extended withinthe lumen of the body passage 38. The individual fibers or groups offibers 84 are spaced apart to thereby allow for the flow 155 of fluidthrough and around the stent body 36 as the stent body 36 appliesoutward pressure to the interior surface 45 of the body passage 38.

[0053] The relationship between the length and the diameter of the stent30 of the present invention is illustrated in FIGS. 19-21. The stent 30in the “at rest” or natural, relaxed condition is illustrated in FIG. 19with a fully expanded, maximum diameter 172. Due to the naturallyoccurring relationship of the fibers or elements 84 of a woven orbraided tubular structure 111 (FIG. 10), a change in length 170 willaccompany any change in diameter 172. Conversely, any change in length170 precipitates a commensurate change in diameter 172. The presentinvention harnesses this relationship to facilitate the placement,maintenance, and removal of the stent 30. As presently embodied, thelength 174 and the diameter 176 of the retention member 48 changesomewhat proportionally to changes in the length 170 and diameter 172 ofthe stent body 36.

[0054] With reference to FIG. 20, as the stent 30 is stretched orextended in length 180, 181, the diameters 182 of the stent body 36 andthe diameter 186 of the retention member 48 are both reduced. Uponremoval or relaxation of the stretching or extending force, the stent 30attempts to assume an original “thermally set” or natural conditionwithin the body passage. Accordingly, the length 190 and the diameter192 increase from the length 180 and the diameter 182 of FIG. 20, asillustrated in FIG. 21. Similarly, the length 191 and the diameter 196of the retention member 48 increase. The increased diameters 192, 196exert radially outwardly directed forces upon any resistive structure.As the diameters 192, 196 increase, the lumen within the body passage 38will also increase, thereby facilitating further increases in thediameters 192, 196.

[0055] The intimal tissue of the body passage 38 responds to thepresence of the braided material of the stent 30 by moving away from thebraided material. In doing so, the lumen of the body passage 38 enlargesitself in response to the presence of the stent 30. As the lumenenlarges, the self-expanding stent 30 follows the inner surface of thebody passage 38 and continues to expand. This, in turn, stimulatesfurther enlargement of the lumen of the body passage 38. The expansionresponse development continues until a maximum lumen diameter isachieved. The expansion/response reaction is believed to be a reactionto the crossing members of the braided material and the motion of thesecrossing members within the body passage 38, especially when the bodypassage comprises a ureter. The expansion/response reaction may also beattributed to a general foreign body reaction within a body passage 38.In the particular case of a ureter, it is believed that the irritationfrom the braided or woven members causes the response. In thisparticular case, the braided or woven material of the stent 30 performsa majority of the work.

[0056] Although an exemplary embodiment of the invention has been shownand described, many other changes, modifications and substitutions, inaddition to those set forth in the above paragraphs, may be made by onehaving ordinary skill in the art without necessarily departing from thespirit and scope of this invention.

What is claimed is:
 1. A stent for use in a body passage/comprising: anexpandable tube having a proximal tube end, a distal tube end, and alumen extending from the proximal tube end to the distal-tube end, theexpandable tube being configurable between a large-diameter relaxedstate and a small-diameter tension state, the proximal tube end and thedistal tube end being separated by a predetermined distance when theexpandable tuber is in the large-diameter relaxed state, and theproximal tube end and the distal tube end being separated by a seconddistance, which is larger than the predetermined distance, when theexpandable tube is in the small-diameter tension state; and a retentionmember integrally formed with the expandable tube and extendingproximally from the distal tube end, the retention member having alarge-diameter relaxed shape and a small-diameter tension shape, andhaving a retention-feature diameter in the large-diameter relaxed shapewhich is greater than an expandable-tube diameter of the expandable tubewhen the expandable tube is in the large-diameter relaxed state.
 2. Thestent as recited in claim 1, further comprising activating means adaptedfor increasing a distance between the proximal tube end and the distaltube end, to thereby change the expandable tube from the large-diameterrelaxed state to the small-diameter tension state.
 3. The stent asrecited in claim 2, the activating means further being adapted forchanging the retention member from the large-diameter relaxed shape tothe small-diameter tension shape, by increasing a distance between theproximal tube end and the distal tube end.
 4. The stent as recited inclaim 3, the activating means comprising: a compression tube adapted forfitting within the lumen and for contacting the distal tube end, thecompression tube further being adapted for applying a distal force ontothe distal tube end when a proximal force is applied to the proximaltube end.
 5. The stent as recited in claim 4, the application of boththe distal tube force to the distal tube end, and the proximal force tothe proximal tube end changing the expandable tube from thelarge-diameter relaxed state to the small-diameter tension state, and aremoval of both the distal force from the distal tube end and theproximal force from the proximal tube end changing the expandable tubefrom the small-diameter tension state to the large-diameter relaxedstate.
 6. A stent for use in a body passage, comprising: a woven tubehaving a proximal tube end, a distal tube end, and a lumen extendingfrom the proximal tube end to the distal tube end; and a retentionmember integrally formed with the woven tube and extending proximallyfrom the distal tube end, the retention member having a diameter whichis greater than a diameter of the woven tube.
 7. The stent as recited inclaim 6, the woven tube being configurable between a insertionconfiguration having a long-length and a small diameter, and a stentconfiguration having a short-length and a large-diameter.
 8. A stent foruse in a body passage, comprising: an expandable tube having a diameter,a proximal tube end, a distal tube end, and a lumen extending from theproximal tube end to the distal tube end; and activating means adaptedfor decreasing the diameter of the expandable tube by increasing adistance between the proximal tube end and the distal tube end.
 9. Thestent as recited in claim 8, the expandable tube comprising a braidedthermoplastic material, and the activating means comprising means forapplying tension between the proximal tube end and the distal tube end,to thereby increase the distance between the proximal tube end and thedistal tube end.
 10. The stent as recited in claim 8, the activatingmeans being adapted for fitting within the lumen.
 11. A stent,comprising: a stent body formed of a braided material; and anenlarged-diameter retention member adjacent to the stent body andintegrally formed with the stent body of the braided material.
 12. Theretention member as recited in claim 11, the enlarged-diameter retentionmember being disposed near a distal end of the stent.
 13. The retentionmember as recited in claim 12, the enlarged-diameter retention membercomprising a cone shape.
 14. The stent as recited in claim 12, furthercomprising: a rigid collar at a distal end of the cone-shaped retentionmember, the rigid collar defining an aperture; and a compression sleeveadapted for fitting within the stent body, and for contacting the rigidcollar.
 15. The stent as recited in claim 14, the stent beingconfigurable into the insertion configuration by application of distalforce on the rigid collar by the compression sleeve, and beingconfigurable into the stent configuration by removal of the distal forcefrom the rigid collar.
 16. The stent as recited in claim 15, furthercomprising a guidewire adapted for fitting within the stent body andthrough the aperture.
 17. The retention member as recited in claim 13,further comprising a plurality of convolutions disposed on the stentbody.
 18. The retention member as recited in claim 11, theenlarged-diameter retention member forming a convolution, which isdisposed near an intermediate portion of the stent.
 19. The retentionmember as recited in claim 18, further comprising a plurality ofconvolutions disposed adjacent to the convolution.
 20. The retentionmember as recited in claim 19, the plurality of convolutions covering amajority of the stent.
 21. The stent as recited in claim 11, the stentbeing configurable between an insertion configuration having along-length and a small diameter, and a stent configuration having ashort-length and a large-diameter.
 22. The stent as recited in claim 21,a ratio of a diameter of the enlarged-diameter retention member to adiameter of the stent body, in the stent configuration, beingapproximately equal to a ratio of a diameter of the enlarged-diameterretention member to a diameter of the stent body, in the insertionconfiguration.
 23. A tube operable as a stent, the tube comprising: aproximal tube end; a distal tube end; a lumen extending from theproximal tube end to the distal tube end; and a collar disposed at thedistal end, the collar being adapted for receiving a distal force fromwithin the lumen, the tube being transformable from a short-length,large-diameter stent configuration to a long-length, small-diameterinsertion configuration when the distal force is applied to the collar,and the tube being transformable back into the short-length,large-diameter stent configuration when the distal force is removed. 24.The tube as recited in claim 23, the tube further comprising: a wallformed of a braided material; and a retention member formed in the wallof braided material, the retention member comprising aradially-increasing portion and a radially-decreasing portion.
 25. Thetube as recited in claim 24, the radially-increasing portion extendingsubstantially perpendicularly to a portion of the wall around acircumference of the wall, and the radially-decreasing portioncomprising a cone shape having an axis parallel with an axis of thetube.
 26. A retention member for use in combination with a stent,comprising: a tubular trunk formed of a braided material; aradially-increasing portion formed in the braided material and disposedadjacent to and integral with the tubular trunk, the radially-increasingportion extending substantially perpendicularly to a surface of thetubular trunk around a circumference of the tubular trunk; and aradially-decreasing portion formed in the braided material and disposedadjacent to and integral with the tubular trunk.
 27. The retentionmember as recited in claim 26, the radially-increasing portion and theradially-decreasing portion forming a cone shape having an axis parallelwith an axis of the tubular trunk.
 28. The retention member as recitedin claim 27, further comprising a plurality of convolutions disposed onthe stent.
 29. The retention member as recited in claim 26, theradially-increasing portion and the radially-decreasing portion togetherforming a convolution, which is disposed at an intermediate portion ofthe stent.
 30. The retention member as recited in claim 29, furthercomprising a plurality of convolutions disposed adjacent to theconvolution.
 31. The retention-member as recited in claim 30, theplurality of convolutions covering a majority of the stent.
 32. A stent,comprising: a radially-contractible tube having a proximal tube end, adistal tube end, a diameter, and a lumen extending from the proximaltube end to the distal tube end; and an actuator disposed within thelumen for increasing a distance between the proximal tube end and thedistal tube end, to thereby reduce the diameter of theradially-contractible tube.
 33. A method of accessing a body passage,comprising the following steps: converting a stent into a long-length,small-diameter insertion configuration by applying tension between aproximal end of the stent and a distal end of the stent, to therebyincrease a distance between the proximal end of the stent and the distalend of the stent; inserting the stent into a body passage of a patient;moving the stent through the body passage of the patient to a desiredlocation; and converting the stent into a small-length, large-diameterstent configuration by removing the tension to thereby decrease thedistance-between the proximal end of the stent and the distal end of thestent.
 34. A method of making an stent, which is transformable between alarge-diameter configuration and a small-diameter configuration, thestent being transformable from the large-diameter configuration to thesmall-diameter configuration upon application from a compression sleeveof a distal force onto a distal end of the stent, the method comprisingthe following steps: providing a woven tubular structure; placing thewoven tubular structure over a forming tool, the forming tool comprisinga cylindrical body having a first diameter corresponding to thelarge-diameter configuration, and having a second diameter that issmaller than a diameter of the compression sleeve; irradiating the woventubular structure with thermal energy, to thereby set a portion of thewoven tubular structure at the first diameter and to set a distal end ofthe woven tubular structure at the second diameter; and removing aresulting structure from the forming tool.
 35. The method as recited inclaim 34, the forming tool comprising a cone-shaped portion near adistal end of the cylindrical body, and the second diametercorresponding to a diameter of a guidewire.
 36. The method as recited inclaim 34, the irradiating step being preceded by a step of folding aportion of the woven tubular structure, located proximally of thecone-shaped portion, proximally upon the cylindrical body to therebyform a retention member.
 37. The method as recited in claim 34, theforming tool comprising a cylindrical mandrel with both a firstcone-shaped portion near a distal end of the cylindrical mandrel and asecond cone-shaped portion near a proximal end of the cylindricalmandrel, and the irradiating step being preceded by the following steps:folding a portion of the woven tubular structure, located proximally ofthe first cone-shaped portion, proximally upon the mandrel to therebyform a first retention member; and folding a portion of the woventubular structure, located distally of the second cone-shaped portion,distally upon the mandrel to thereby form a second retention member. 38.The method as recited in claim 37, the removing step being followed by astep of cutting the resulting structure in half, to thereby bisect theresulting structure into two stents.
 39. A method of iterativelyincreasing a diameter of a lumen of a body passage, comprising thefollowing steps: inserting a stent into a body passage of a patient;moving the stent through the body passage of the patient to a desiredlocation; and iteratively increasing a diameter of the stent, a firstiterative increase of the diameter of the stent resulting in thediameter, and a second iterative increases of the diameter of the stentresulting in the diameter of the lumen increasing to a second enlargeddiameter which is greater than the first enlarged diameter.
 40. Themethod as recited in claim 39, the inserting step being preceded by astep of converting the stent into a long-length, small-diameterinsertion configuration by increasing a distance between a proximal endof the stent and a distal end of the stent.
 41. The method as recited inclaim 40, the step of iteratively increasing a diameter of the stentincluding a step of converting the-stent into a small-length,large-diameter stent configuration by decreasing a distance between aproximal end of the stent and a distal end of the stent.